This invention relates generally to radiotelephones and, in particular, to mobile stations such as those capable of operation with a cellular network or with a personal communications network (PCN).
The so-called Short Message Service (SMS) is a Teleservice specified in some modern cellular communications systems, for example IS-136, for enabling a user to send messages to, and receive text messages from, the communications network. The SMS attempts to deliver a message to a mobile station (MS) whenever the mobile station is registered to the network, even when the mobile station is engaged in a voice or data call. The mobile station may roam throughout the network and still be capable of sending and receiving messages. As presently specified in IS-136.1, a mobile station configured for SMS provides methods for the user to receive, read, clear, send, and save messages.
The IS-136 specification presently enables both mobile station terminated (network to mobile station) and mobile -station originated (mobile station to network) SMS. The SMS Point-to-Point, Paging and Access Response Channel (SPACH) is specified for use in the mobile station terminated SMS mode. As is specified in IS-136.1 Rev. A, Mar. 21, 1996, Section 7.1.1.2.1 and Section 7.1.2.2, a SMS Submit message is also defined for sending a SMS message from the mobile station. The SMS Submit message is specified to be sent to the network, more particularly to the Base Station/Mobile Switching Center/Interworking Function (BMI), in an R-DATA message. The R-DATA message is sent on a reverse (i.e., MSxe2x86x92BMI) digital control channel.
It can be appreciated that the use of the reverse digital control channel to send the mobile station originated SMS messages has the disadvantage of consuming a valuable system resource that could otherwise be used to convey signalling information for, by example, mobile station registration and call origination purposes. Typically, there are significantly fewer digital control channels assigned in a wireless communications system than there are traffic (e.g., voice and/or data) channels. While the use of the digital control channel may not be especially disadvantageous for one mobile station transmitting a relatively short SMS messages (e.g., less than about 200 characters), if several mobile stations were simultaneously transmitting longer SMS messages the overall system capacity can be reduced.
Furthermore, existing Teleservices place restrictions on the length of messages that can be transmitted from a mobile station using the R-DATA message. Such restrictions can be a significant disadvantage when it is desired to transmit a message that exceeds the specified maximum length of the R-DATA message for a particular system.
More particularly, and referring specifically to the IS-136 air interface, Teleservices are supported for SMS and Over the Air Service Provisioning, that is, Over-the-Air Activation Teleservices (OATS). Other Teleservices are envisioned in the future. These Teleservices utilize the Layer 3 R-DATA message to transport their transactions over the air interface. At the BMI the R-DATA message is translated into a Short Message Delivery Point-to-Point (SMDPP) message for relay through the IS-41 network. These two mechanisms (R-DATA and SMDPP) can each impose constraints on the size of a Teleservice or Application transaction. It would thus be desirable to provide a method to free the Teleservice definition from these arbitrary constraints. In fact, these constraints may be so onerous that they may effectively shut a particular Teleservice down.
In IS-136 the BMI may limit the size of R-DATA messages through the R_Data_Message Length information element provided in the Fast Broadcast Control Channel (F-BCCH) Access Parameters message. This currently allows the BMI to limit mobile station originated R-DATA messages to either 31, 63, 127, or xe2x80x9cLimited only by layer 2 formatxe2x80x9d (which provides approximately 250) bytes in length. There is also a proposal to define a new value that provides an air interface limit that conforms to the largest user data space that may be accommodated into one IS-41 SMDPP message. This is currently expected to be approximately 204 bytes.
It is thus an object of this invention to provide a wireless communications system that implements a mobile station originated Teleservice function, such as SMS, without the use of a reverse digital control channel.
It is a further object of this invention to provide a cellular communications system that implements a mobile station originated Teleservice function, such as SMS, through the use of a digital traffic channel which is normally allocated for voice and data transmissions.
It is another object of this invention to provide a method for effecting signalling between a mobile station and a BMI so as to enable a reverse digital traffic channel to be used to convey a Teleservice message, and to avoid the use of a vocoder or data modem that would typically be connected to the traffic channel by the BMI.
It is one further object of this invention to provide a method for message transmission that is unconstrained by R-DATA or SMDPP message length restrictions.
The foregoing and other problems are overcome and the objects of the invention are realized by methods and apparatus in accordance with embodiments of this invention.
A method of this invention is disclosed for operating a user terminal, such as a cellular radiotelephone, of a type that is bidirectidnally coupled to a network through an RF interface. The method includes a first step of storing at least one message in a memory accessible by the mobile station. A second step transmits a Teleservice (e.g., SMS) origination request from the mobile station to the network using a reverse digital control channel. The request specifies that a reverse digital traffic channel be assigned to the mobile station. A next step, executed in response to being assigned to a reverse digital traffic channel, transmits the at least one stored message to a SMS center that is coupled to the network, the at least one stored message being transmitted over the assigned reverse digital traffic channel.
In a preferred embodiment of this invention the Teleservice origination request is transmitted using a random access channel, the step of transmitting the at least one stored message includes a step of bypassing a voice coder and a data modem within the mobile station, and the step of transmitting the at least one stored message is accomplished in an Automatic Retransmission Request (ARQ) mode of operation.
In one embodiment of this invention the mobile station transmits an origination message having both Voice Mode and Data Mode fields set so as to inform the BMI that neither a vocoder or data modem are required to receive the mobile station""s transmission. Having configured the BMI to receive a mobile station originated SMS transmission, the mobile station 10 transmits the SMS message on a digital traffic channel that is assigned by the BMI. In response, the BMI receives and demodulates the mobile station transmission and routes the received user data unit, along with appropriate identification and support information, to the SMS message center for subsequent processing in a conventional manner.
Further in accordance with this invention there is described a method to deliver Teleservices in a wireless communications system that are not constrained by any message length limitations imposed by the air interface or network layers supporting the wireless service. The method applies compression, encryption, segmentation and assembly services, end to end acknowledgment, retransmission of segments, and error detection and retransmission of the entire Teleservice transaction. This process is referred to herein as a Teleservice Transmission Service or TTS.
In accordance with this aspect of the invention a method is disclosed for operating a wireless communications network to transmit a Teleservices message from a source to a destination. The method includes the following steps:
(a) inputting to a Teleservice Transmission Service (TTS) a Teleservices message to be transmitted, the Teleservices message being input through a first TTS Service Access Point (SAP); (b) partitioning the Teleservices message into a plurality of smaller message segments each having a maximum size that is equal to or less than a specified maximum length of a message unit (e.g., an R-DATA message data length) for a DCCH message transport facility; and (c) outputting the message segments from the TTS through a second TTS SAP to an air interface service for transmission to the destination. The method further includes optional steps of compression and/or encrypting the Teleservices message and then (d) transmitting a first message from the source to the destination for specifying at least a total number of message segments to be transmitted, the first message also conveying a first message segment; (e) transmitting one or more second messages from the source to the destination, each second message conveying a further message segment and also specifying at least a number of remaining message segments; and (f) transmitting a final message from the source to the destination, the final message conveying a last message segment and also specifying the end of the Teleservices message.
Although described primarily in the context of the SMS Teleservice, it should be appreciated that the teaching of this invention applies as well to other types of Teleservices, including OATS, and also future Teleservices.